docs: def _to_fields(self, data):
          '''
          Return generator over the (numerical) PLY representation of the
          list data (length followed by actual data).
  
          '''
          (len_t, val_t) = self.list_dtype()
  
          data = _np.asarray(data, dtype=val_t).ravel()
  
          yield _np.dtype(len_t).type(data.size)
          for x in data:
              yield x